System for Visual and Electronic Reading of Colorimetric Tubes

ABSTRACT

Gas detector tubes may be used to determine a concentration of target gases in air. The gas detector tubes described may be read either by and optical reader or visually by the user. A gas detector tube reader having an optical reader capable of reading a length of stain, a color change and color density of a reagent in a gas detector tube. The gas detector tube may further comprise sensors for measuring the environmental conditions during sampling.

RELATED PATENT APPLICATIONS

This patent application claims priority under 35 U.S.C. §119 to U.S.Provisional Patent Application No. 61/380,582 filed on Sep. 7, 2010which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to gas detector tubes and an apparatus forsampling. Embodiments of the apparatus are capable of detecting anddetermining an approximate concentration of at least one component of agas mixture. Embodiments of the apparatus comprise a system forcolorimetric detection of certain components of a gas by color change ofa chemical reagent. The resulting color change may be optically measuredas a length-of-stain that is proportional to the reacted quantity of thetarget gas or as a level of color difference between unchanged andchanged by chemical reaction color. In embodiments of the gas detectortube, the length of stain and/or color change may be determined visuallyor electro-optically.

BACKGROUND OF THE INVENTION

There are a variety of apparatuses for measuring the concentration ofcertain gaseous components of a gas mixture. One simple apparatuses,referred to as gas detector tubes or gas indication tubes, typicallycomprise a glass or other transparent tube and a chemical reagent thatis capable of reacting with a target chemical compound resulting in acolor change of the reagent.

Conventional gas detector tubes are glass tube filled with a chemicalreagent that reacts to a specific chemical or family of chemicals. Thechemical reagent is sealed within the glass tube and retained inposition by gas permeable plugs on either end of the glass tube. In somecases, the chemical reagent may be liquid impregnated into a porouschemically neutral solid substrate. The chemical reagent is protectedfrom exposure to contaminants and chemical compounds by sealing thetubes at each end until use and, therefore, extending the shelf life. Touse the gas detector tube, the tips are broken to open a flow paththrough the tube and across the reagent. The air to be sampled may thenbe drawn through the tube and in contact with the reagent using a fixedvolume sampling pump, for example. The reagent layer is capable ofrapidly reacting with the target chemical compounds as the air to besampled is drawn through the tube. The amount of reaction and the changeof color of the reagent are related to the concentration of the targetchemical compounds in the sampled gas and the volume of gas drawnthrough across the reagent.

To determine the gas concentration, a known volume of gas may be drawninto the tube and the concentration of the gas is the only variable. Thelength of the color change or the degree of color change of the reagentthen corresponds to the concentration of the target compounds. Detectortubes that measure gas concentration by length of stain or length ofcolor change are reliable and simple to use. Currently, detector tubesrelying on measurement of the intensity or density of the generatedcolor are not used because of difficulties in creating an appropriateset of color standards to indicate the concentration of the gas.

After manufacturing a batch of length of stain detector tubes, knownconcentrations of target gases are passed through the gas detector tubesto develop a batch specific a calibration curve relating the length ofstain to a corresponding gas concentration. The calibration curve isincluded with the detector tube to allow visual reading of theconcentration of a gas in a sampled volume. From their firstintroduction the detector tubes have their scale printed separately,see, for example, U.S. Pat. No. 2,174,349 to J. B. Littlefield. As theleading edge of color change of the reagent in the detector tubes is notalways well defined, the scale divisions may be marked having a distancegreater than length of diffusive front of discoloration. As such, thescales are of poor resolution and, more recently, the scales printeddirectly on the surface of the tube. For example, Dreager™, Gastec™,Kitagava™, Auer™, MSA™, RAY™, as well as other manufacturers of detectortubes have on their tubes the beginning of the scale—first scaledivision, marked 3 to 5 mm from the end the first input plug. Because ofpossible channeling effects, resulting in different lengths visible oneach side of the tube, the divisions are printed as rings around thetube and numbers representing concentrations are in close proximity orinto broken portion of the ring. The drawback of the known art is thatsuch detector tubes cannot be read by electronic device because of theconcentration lines, concentration amounts, and other marks on the tubesobstructing optical reading of the length of stain. For example, themarkings may be interpreted by the device as a color change.

There has been a long felt need for a better more accurate and objectiveway of reading gas concentration with gas detector tubes. Heim et al. inU.S. Pat. No. 4,123,227 show a length-of-stain tube electronic readerbased on detector tube without any printed matter. The detector tubeserves as an alarming device and is periodically interrogated over aperiod of time. Leichnitz et al. in U.S. Pat. No. 5,069,879 suggested atube having no scale on the readable part of the surface and printedmeans introducing into electronic reader all specific data for the tubeincluding calibration data. There is a significant drawback of the tubesmanufactured to be read by electronic reader only; they may not also byread visually.

The contemporary art of colorimetric reading devices is developed in thedirection of devices even more specifically designed foroptic-electronic reader. U.S. Pat. No. 5,089,232 to May shows anarrangement of tube-like devices for only electronic reading. U.S. Pat.No. 5,397,538 to Stark et al., U.S. Pat. No. 5,415,838 to Rieger et al.and U.S. Pat. No. 5,464,588 to Bather at al. depict development ofspecific tube-like devices for electronic reading of a zone ofdiscoloration. Such devices however are highly specific and cannot beread without specialized electronic means.

All color change indicated by colorimetric reactions of the reagentdepend to some extend on the ambient conditions—temperature, relativehumidity and barometric pressure.

Temperature and relative humidity correction factors are typicallyprovided by the manufacturer for a specific reagent and target compound.Like calibration curves the correction factors may be calculated on abatch basis. The correction factors should be applied to theconcentration indicated by the length of stain in the detector tube andto more accurately determine the actual target gas concentration. Theatmospheric pressure has two components altitude above sea level andweather factors. The altitude component is generally a larger factor indetermination of the atmospheric pressure than the weather factors(usually much less than 1%). Weather factors may be considerednegligible. The altitude of the gas detector above sea level, however,may have a significant outcome on determination of the actualconcentration. In some cases, the measured concentration may beconsiderably below of the actual concentration.

TABLE 1 Atmospheric Pressure Function of Altitude Altitude Pressure (km)(mb) Correction 0.0 1013.25 100.0% 0.5 954.61 94.2% 1.0 898.76 88.7% 1.5845.59 83.4% 2.0 795.01 78.4% 2.5 746.91 73.7% 3.0 701.21 69.2% 3.5657.80 64.9% 4.0 616.60 60.8% 4.5 577.52 56.9% 5.0 540.48 53.3% 5.5505.39 49.8%

Typical detector tubes also show an increasing sensitivity to colorchange with an increase in temperature. Therefore, gas detector tubesmay also require compensation for temperature. The following table,Table 2, shows the temperature compensation factors for a Gastec™ gasdetector tube for determination of the concentration of 1, 1trichloroethylene in air:

TABLE 2 Temperature, ° C. 0.0 10 20 30 40 Correction factor 1.4 1.3 1.00.8 0.65

The following table, Table 3, shows the compensation factors for aparticular gas detector tube manufactured by Gastec for determination ofthe concentration of hydrazine in air:

TABLE 3 Relative Humidity % 10 30 50 70 90 Correction factor 0.8 0.9 1.01.2 1.4

Determination of a more accurate estimation of an actual concentrationusing gas detector tube should incorporate one or more of thesecompensation factors for environmental conditions. There is a need for ameasurement system that provides automatic compensation of theseparameters.

SUMMARY

Embodiments of the gas detector tubes may be read either visually or byan electronic gas detector tube reader with any obstruction of thereagent. Further, embodiments include gas detector tubes comprising agas detector tube surface that does not comprise marking or shading thatobstruct view of at least a portion of the reagent. The detectors maycomprise 2 to 4 different scales for visual reading of the gasconcentration on extensions or scale wings of the gas detector tubes.The extensions or scale wings provide a sufficient surface area for avariety of visually and optically or electronically readableinformation. The scales may be for 1-5 strokes, or more, an appropriategas detector pump and/or in two formats such as, but not limited to,mg/m³ and ppm. In addition to the scales, the gas detection tubes mayfurther comprise optical information for the calibration of a datareadable optic-electronic gas detector tube reader. In an embodiment,the gas detector tube comprises a sealed transparent tube, a chemicalreagent capable of a colorimetric reaction with a gaseous chemicalcompound within the sealed transparent tube, at least one elongatedextension or wing scale extending from the tube; and at least one lengthof stain measurement scale on the extension. The gas detector tube mayfurther comprise a transparent plastic adhered to a surface of thetransparent tube and a surface of the elongated extension. Embodimentsalso include an optic-electronic gas detector tube reader capable ofreading such detector tubes such as by comprising an optical reader. Asused herein, an “optic-electronic reader” or an “optical reader” is acomputer device that captures visual information and translates theimage into digital information the computer is capable of understandingand displaying. The visual information may be two or three dimensionalinformation and include the color and shape of visual information. The“optic-electronic reader” or an “optical reader” may includeilluminating device and a light sensor for interpreting the lightreflected from an object. As used herein, “visual” means as interpretedby the human eye and brain.

Embodiments of a gas detector tube reader may comprise a holder forreceiving a gas detector tube, an information reader capable of readingelectronic or optically coded information from the gas detector tube, anoptical reader system capable of determining the length of stain in thegas detector tube, and a central processing unit to estimate the targetgas concentration from the outputs of the sensors. Embodiments of theoptic-electronic gas detector tube reader are capable of compensatingfor any effects on reading as a result of relative humidity, temperatureand altitude.

The optic-electronic gas detector tube reader can read the variouscalibration data from each gas detector tube. The calibration data,measured data and compensated data may then be output and displayed on adisplay of the optic-electronic gas detector tube reader and/orcommunicated to another processing unit for display and recordation. Thedata may include, but is not limited to, the type of tube, target gases,measuring range of the tube, tube accepted/rejected upon introduction ofan internal standard and/or expiration date, concentration measured,environmental conditions including, but not limited to, relativehumidity, temperature, barometric pressure, as well as total % ofcompensation applied to the measured gas concentration.

Embodiments of the method of determining a concentration of a gaseouscompound, comprising placing a tube in an optic-electronic gas detectortube reader, electronically reading information from the gas detectortube, and displaying an acceptance or rejection of the tube based uponthe expiration date of the tube and/or any prior discoloration of thereagent. The method may further comprise drawing a known volume of gassample through the gas detector tube and optically reading the length ofstain. After sampling, if applicable, the readout of theoptic-electronic gas detector tube reader may display informationincluding, but not limited to, a measured gas concentration, thecompensation factors to be applied to the measured gas concentration,each compensation factor determined from a measurement of the ambientconditions sensors including, but not limited to, temperature, relativehumidity and barometric pressure or altitude, for example.

Embodiments of the gas detector tubes and gas detector tube readersallow use of the gas detection by gas detector tubes both visually andoptic-electronically and allow a more accurate and flexible way ofutilizing the gas detector tubes.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. As used herein, the singularforms “a,” “an,” and “the” are intended to include the plural forms aswell as the singular forms, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, steps, operations, elements, components, and/or groupsthereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by onehaving ordinary skill in the art to which this invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

In describing the invention, it will be understood that a number oftechniques and steps are disclosed. Each of these has individual benefitand each can also be used in conjunction with one or more, or in somecases all, of the other disclosed techniques. Accordingly, for the sakeof clarity, this description will refrain from repeating every possiblecombination of the individual steps in an unnecessary fashion.Nevertheless, the specification and claims should be read with theunderstanding that such combinations are entirely within the scope ofthe invention and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with the reference to the drawingswherein:

FIG. 1-A to 1-E depicts colorimetric gas detector tubes comprising atleast one extension or scale wing; wherein FIG. 1-A is a perspectiveview of the tube assembly with planar extensions, FIG. 1-B is across-section of the tube assembly with two scale wings; FIG. 1-C is across-section of the tube assembly with one scale wing; FIG. 1-D is agas detector tube with prismatic cross-section with scales along thewalls or along the edges of prism; FIG. 1-E is a cross-section of gasdetector tubes attached on the holder for transportation and storage;

FIG. 2 depicts a front view of colorimetric gas detector tube assemblywith sidewise scales;

FIG. 3 depicts a reading head assembly of a gas detector tube reader;

FIG. 3-A is a perspective view of the two shells (jaws) of the readinghead of a gas detector tube reader;

FIG. 3-B is a cross-section of the jaws over a gas detector tube withmarked direction of light;

FIG. 4 is a perspective view of piston pump unit connected to a gasdetector with tube reader and gas detector tube secured in the holder;

FIG. 5-A and 5-B are a cross-sections of the reading head assembled onthe pump in two positions: FIG. 5-A Front of tube with scale wings andFIG. 5-B is a side view of scale wings in locked position;

FIG. 6 is an electrical schematic diagram of optic-electronic readingunit reader depicting the electrical connections between the centralprocessing unit the sensors and other components;

FIGS. 7-A and 7-B shows graphs representing point of stopping andintegration for three basic working modes of the reading deviceintegrated to piston type hand pump; FIG. 7-A shows the process cycle ina fixed range and predetermined fixed sampling volume, B and B1 arepoints of color saturation followed by immediate integration at veryhigh concentration before end of stroke—point A and FIG. 7-B is aprocess cycle in very low concentration mode urging user to perform morestrokes until first color change is detected—points C and C1 and FIG.7-C is a graph showing a vacuum pressure check mode.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Gas detector tubes may be used to determine the concentration of atleast one target gas, family of target gases comprising a similarfunctional group, or class of target gases (collectively “target gases”)in a sample gas. The gas detector tubes typically comprise a chemicalreagent within a transparent tube. Gas detector tube may comprise one ormore chemical reagents that indicate the presence of specific targetgases. Typical chemical reagents for gas detector tubes comprise aporous solid with pathways that allow gas to flow through the poroussolid from an inlet of the gas detector tube to an outlet of the gasdetector tube or the chemical reagent is on the surface of a poroussolid substrate. The chemical reagent will change color when the reagentis in contact with the chemical reagent (“colorimetric reaction”),typically the chemical reagent and the target gases will react resultingin the color change. As a sample passes through the gas detector tube,the target gases are involved in the colorimetric reaction with thechemical reagent until the target gases are depleted from the sampledgas. Many reagents for use in gas detector tubes are known andapplicable to embodiments of the gas detector tubes. A sample istypically drawn through the gas detector tubes by a sampling pump.Common sample pumps include hand-held piston pumps or bellows pump thatare capable of accurately and repeatedly drawing a known volume of air.

Typically, the chemical reagent is fixed in place within the tube by twoporous solid plugs at either end of the reagent. As the gas comprisingtarget gases is drawn through an inlet of the gas detector tube, thechemical reagent near the inlet will begin to change color and, if theconcentration of the target gases is with the readable range of the gasdetector tube, the chemical reagent near the exit of the tube willremain unchanged. The length of the color change of the reagent (“lengthof stain”) within the tube will correspond to the total amount of thetarget gases that were passed through the gas detector tube. In a knownvolume of gas is passed through the tube, a concentration of the targetgases may be determined. Conventional gas detector tubes have a scaleprinted on the glass tube over the chemical reagent that may be used toapproximate the concentration of the target gases for a known volume ofthe sampled gas. Each gas detector tube will have a readableconcentration range of target gases, if the gas concentration range isexceeded for a volume of sample, the chemical reagent will change colorthroughout its entire length and a concentration of the target gas maynot be conventionally determined or if the concentration of the targetgas is too low, the chemical reagent may not record a sufficient colorchange to determine the concentration of target gases. In such cases, adifferent tube with the appropriate concentration range may be used orthe volume of sampled gas may be increased or decreased to produce areading within the scale. For some gas detector pump and gas detectortube systems, up to a five-fold increase in sampled volume isrecommended. The scale of the gas detector tube must then be adjusted toaccount for the different sample volume.

Embodiments of the gas detector tubes of the invention may be readeither electronically by an electronic gas detector tube reader orvisually by a user by a simple comparison of the length of stain withone or more scales on an extension of the transparent body. Specificembodiments of the gas detector tubes comprise a sealed transparenttube; a chemical reagent capable of a colorimetric reaction with atarget gas within the sealed transparent body and at least one elongatedextension extending from the body comprising both electronicallyreadable indicia and visually readable indicia. Unlike conventional gasdetector tubes, the indicia are not on the transparent body and,therefore, will not interfere with electronic reading of the length ofstain. Embodiments include gas detector tubes comprising a transparenttube or transparent body surface that do not comprise marking or shadingthat obstruct view of at least a portion of the reagent foroptic-electronic reading of the length of stain.

Embodiments of the gas detector tubes may further comprise a transparentplastic covering adhered to the surface of the body. The extensions maybe formed from the transparent plastic covering or the extensions mayalso be covered by the transparent plastic covering.

Gas Detector Tubes

The gas detector tubes may comprise a transparent tube. During storageand prior to use the transparent tube may be a sealed tube. As usedherein, “tube” means a conduit defining a flow path of anycross-sectional shape. The cross-sectional shape may be circular, oval,rectangular, square, rectangular, polygonal or any desiredcross-sectional shape. As used herein, “sealed tube” means the tube isclosed such that it creates an inner volume within the sealed tube thatis not substantially exposed to an environment external to the tube. Thetube may be sealed simply by heating and pinching the ends of the tubesto seal the tube, using caps, septums or other means to seal the tube.Embodiments of the gas detector tubes may comprise a transparent tubemade from a glass or transparent plastics such as but not limited to,acrylic, polycarbonates, copolymers of polyethylene and polypropylene,polyesters as well as other transparent materials.

In further embodiments, the gas detector tube may comprise a transparenttube and a transparent plastic adhered to a surface of the transparenttube. For example, the outer surface of the transparent tube may bewrapped by thin optically clear conformable plastic adhered by a neutraltransparent adhesive layer. The gas detector tubes may have one or moreextensions or “scale wings”. In some embodiments wherein the indicia areto be optically read by the gas detector tube reader, the extension maycomprise or form pockets for the printed scales, the pockets comprise atransparent window allowing illumination and reading of the codedinformation.

Extensions

The gas detector tubes may further comprise one or more extensions orscale wings. The extensions extend outwardly from the surface of thetransparent tube and form a surface for printing, etching, embossing,attaching, encapsulating, holding, or otherwise providing a scale forreading the length of stain resulting from sampling with the gasdetector tube. The extensions or scale wings may extend substantiallyperpendicular from the transparent tube surface or a tangent to thetransparent tube surface. As used herein, “substantially perpendicular”means within ten degrees of a ninety degree angle. As the scale isprinted on the extensions, the transparent tube may not comprise anymarkings or shadings to obstruct electronic reading of the color changeor length of stain of a reagent in a sampled tube. The extensions willtypically be at least as long as a usable length of the reagent withinthe tube. In certain embodiments, the gas detector tubes comprise anextension that is an elongated rectangular shape attached to thetransparent tube and extends along a length of the tube at least as longas a distance between the two porous plugs. In embodiments of the gasdetector tubes that are capable of being read both visually and by anelectronic gas detector tube reader, the indicia on the extension orscale wings will comprise both visually readable scale andelectronically readable information is printed on the scale. Inembodiments of the gas detector tubes comprising more than one extensionand scale indicator, any of the extensions may comprise both visuallyreadable scale and electronically readable information or only one ofthe visually readable scale and electronically readable information.

In certain embodiments, the gas detector tube may comprise a pocket forreceiving a scale indicator comprising the indicia. The pocket mayprotect the scale indicator from exposure to the environment. Afterinsertion of the scale indicator, the pocket may be sealed such as by anadhesive.

In additional embodiments, the gas detector tubes may comprise twoextensions. The second extension may provide additional surface area ora second pocket for indicia to be provided on the gas detector tube. Theadditional indicia may include scales with different units of measure,scales for different volumes of sampled gas, a bar code, or otherelectronically readable information, for example. The extensions may bethe same or different shape, the same or different size, in the sameplane, in different planes or in substantially parallel planes. Inembodiments of the gas detector tubes, the extensions and thetransparent tube may be formed as a unitary part or as individual partsattached together. The transparent tube and extensions may be attachedtogether by a transparent covering adhered to both the transparent tubeand the extension or by an adhesive, or melting the parts together, forexample.

As discussed, embodiments of the gas detector tubes are capable of beingread both visually and by an electronic gas detector tube reader, theextensions may comprise a locating system for accurately placing the gasdetector tube in the electronic gas detector tube reader. The locatingsystem may be any components that are capable of aligning the gasdetector tube in the reader. For example, the locating system maycomprise a stops and/or a recess capable of receiving and securing atleast one of the extension or the transparent tube or may simplycomprise a pin and recess. One of the pin and recess may be located onthe gas detector tube and the other of the pin and recess is located onthe electronic gas detector tube reader. For example, one of the scalewings may comprise an oval recess which may be aligned with a pin in areading head of a gas detector tube reader to thereby provide accurateand repeatable position of the tubes for reading.

Transparent Covering

Embodiments of the gas detector tube may further comprise a transparentcovering. The covering may encapsulate at least a portion of thetransparent tube and/or the extensions. The transparent covering may bea plastic that is conformable to at least a portion of an exterior ofthe tube and/or the extensions. The transparent plastic is adhered tothe body by at least one of physical means, shrink wrapping, oradhesive. The adhesive may be a permanent neutral transparent adhesivelayer. However, the transparent plastic should not interfere withreading of the length of stain of the reagent for either visual orelectronic reading of the gas concentration.

The transparent covering may form pockets or otherwise encapsulateand/or secure the extensions to the transparent tube. The pockets may befixed along the main axis of the tube so any scales on the extension maybe retained in position adjacent to the chemical reagent. The scales maybe single or double sided with scale marking on both sides to increasereadability and flexibility in providing information and data.

In some embodiments, the transparent covering or the transparent tubemay be colored similarly to the color of the unreacted chemical reagentor complementary to a color expected after the colorimetric reaction ofthe chemical reagent. Thus, the color of the transparent covering may beused to thereby filter the illuminating and reflected light of anoptically readable gas detector tube reader to enhance the colorcontrast between reacted and unreacted reagent layer and increase theaccuracy of the optical reader. The enhanced contrast may more clearlydefine the reacted portions of the reagent and the end of the length ofstain in the tube may be more easily identified. The design allowsadditional filtration color or complemented color to be superimposed onthe color changing reagent layer thereby increasing visual and opticallyread color contrast between pristine and reacted reagent.

The transparent covering may also comprise a tacky surface for moresecurely holding the gas detector tubes in a box for storage ortransportation.

Printed Scales

The gas detector tubes comprise indicia and/or scales. The indicia maypreferably be on the extensions or scale wings to leave an unobstructedview of the reagent. The visually readable indicia may be used at leastto measure the length of stain produce by the gas detector tube afterpassing a sample through the tube. The length of stain corresponds to anuncompensated concentration of the target gas in the sample. The indiciaand/or scales may be incorporated on the extension by any meansincluding being printed, embossed, or etched directly on the extension,applied to the extensions with a label or card, and/or inserted within apocket of the extension, for example. The scales are made from opaquepreferably white material and positioned parallel to the main axis ofthe gas detector tube. The divisions of each scale may be printed,embossed or etched by any feasible art including laser printers andinkjet printers. As such, any batch to batch manufacturing differencesin the production of the gas detector tubes may be encoded and printedalong with other standard information pertaining to particular type oftube. For embodiments of the gas detector tubes to be electronically oroptically read by a optic-electronic gas detector tube reader, theelectronically or optically readable information may be included on theextensions. The optically readable indicia may be read by the opticalreader, converted to digital information and understood by the centralprocessing unit.

In embodiments of the gas detector tubes for both visual and electronicor optically reading of the tubes, the indicia for each use should notinterfere with each other. For example, one set of information may be onthe front and the other on the back or in different area on the sameside, for example. The electronic or optically coded information mayinclude the type of tube, exposure range, calibration curve, expirationdate, pristine or unreacted color of the reagent, and allowable range ofcolor change after certain edging, expected color change anddensity/saturation of the reacted and unchanged reagent materialnecessary for automated optic-electronic reading.

In addition to the electronically or optically readable information, theprinted scales comprise visually readable information. The visuallyreadable information may include, but is not limited to, type of tube,range of exposure, recommended strokes of sampling, expiration date,part and lot numbers. The scales may further include an indication suchas an arrow, for example, indicating the direction of introducing thetube into reader and/or sampling air through it. In some embodiments,the electronically or optically readable information may be in arelatively small area and/or located in an area different than thevisually readable information. The electronically readable informationmay be optically readable, electronically readable and/or wirelesslyreadable such as by radio frequency identification (RFID), for example.

In some embodiments, the printed scale may be adhered to or within apocket of the extensions by the same adhesive that is used to adhere thetransparent covering to the tube. Thus, the scales may be securelypositioned in the appropriate location relative to the reagent toeffectively allow determine a concentration of a gas in a sample from acolor change in the colorimetric reagent. During the manufacturingprocess the beginning of each zero mark of the scale may be preciselyaligned with the line separating reagent layer from the end of thereagent retaining plug adjacent to the inlet of the tube.

The indicia may include scales for different sampled volumes. Forexample, if a significant colorimetric reaction does not occur from afirst volume of the gas to be sampled, such as a single stroke of apiston sampling pump, additional volume of the gas to be sampled may bedrawn through the gas detector tube. The colorimetric reaction may notbe significant relative to a specific gas detector tube in a colorchange does not occur or the color change does not extend into thereadable concentration scale. In such case, additional volume of gas maybe drawn through the gas detector tube, four more strokes of the pistonmay be used to observe color change, for example. If a color changestill doesn't appear another 5 strokes may be necessary, however, notall types of gas detector tubes allow linear approximation of gasconcentrations to that extent.

For the appropriate types of tubes, the indicia may include four scalesmarks appropriate for required volume of air necessary to produce areadable length of stain in the reagent. The additional scales may be onthe both sides of the extensions. The indicia may also include scale fordetermination of the gas concentration in different units such as, butnot limited to, ppm and/or mg/m³. With the indicia provided on theextensions or scale wings, embodiments of the gas detector tube maycomprise significantly more surface for incorporating information suchas an increased number of scales, larger size scales, greater resolutionof gas concentration readings, and additional information concerning thetype of reagent, compensation factors, expiration date, as well as otherinformation regarding use of the tube.

Indicia

Embodiments of the detectors may comprise indicia that may be readvisually be the user of the gas detector tube and/or electronically oroptically by a gas detector tube reader. For example, the gas detectortubes may comprise 2 to 4 different scales for visual reading of the gasconcentration. The scales may include different sample volumes such as ascale for one stroke of the piston pump, a scale for five strokes of thepiston pump wherein each volume has a scale in different units. Thevisually readable information may further include at least a portion ofinformation selected from the group of information comprising the typeof tube, range of exposure, recommended volume of sampling, expirationdate, part and lot numbers and an indication of the direction of flowduring sampling.

In addition to the scales, the gas detection tubes may further compriseelectronically or optically readable information for the calibration ofa data readable optic-electronic gas detector tube reader, for example.The optically readable information may be comprised in a bar code orother coded information of the information may be both typical visuallyand optically readable information. However, neither the electronicallyreadable indicia nor the visually readable indicia should obstructoptically or visually reading the color of the reagent before samplingor the change of the reagent after sampling. In certain embodiments ofthe gas detector tubes, the indicia includes electronically readableinformation such as the type of tube, the target gases reactive with thereagent, the limits of the gas concentration range, a calibration curve,an expiration date, an unreacted or pristine color of the reagent, andallowable color change range, environmental correction factors ofcurves, an expected color change and color density/saturation of thereacted reagent.

In certain embodiments, the scale divisions may cover at least 80-95% ofthe total length of reagent and optically coded information is imprintedoutside of this range so as to not interfere with visual reading of thegas concentration. The indicia may further comprise a color of thepristine reagent and a color of the reagent after contact with thetarget gases.

Gas Detector Tube Reader

Embodiments of the invention include a gas detector tube reader capableof reading the electronically and/or optically readable information onthe detector tubes and the length of stain in a gas detector tube.Embodiments of the gas detector tube reader may comprise a holder forreceiving a gas detector tube, an information reader capable of readingelectronic or optically coded information from the gas detector tube, anoptical reader capable of determining the length of stain in the gasdetector tube, and a central processing unit. As used herein, a centralprocessing unit (CPU) is a portion of a computer system that carries outthe instructions of a computer program and performs the basicarithmetical, logical, and input/output operations of the system. Theterm central processing unit also includes both distributed processingsystems and multiple central processing units. The CPU is incommunication with a computer memory device capable of storing theoptically or electronically read information from the gas detector tube.As used herein, computer memory refers to the physical devices used tostore programs and/or data on a temporary or permanent basis for use ina computer or other digital electronic device. The computer memorystorage device may be at least one of RAM, DRAM, SRAM, tape, magneticdisk, optical disks, flash memory, compact disk, DVD, and/or addressablesemiconductor memory. A portion of the memory may be read only memoryfor storing information concerning the canister or gas mask that is morepermanent such as, but not limited to, the canister identification, thechemical sorbent in the canister, the compounds capable of beingabsorbed or adsorbed on the chemical sorbent, the amount of chemicalsorbent in the canister, the general capacity of the chemical sorbent,the capacity of the chemical sorbent for a specific target compound, thedate of the manufacture of the canister, and/or the expiration date ofthe canister, for example. Other digital memory may be read/writememory. The term “memory” is often associated with addressablesemiconductor memory, i.e. integrated circuits consisting ofsilicon-based transistors, used for example as primary memory but alsoother purposes in computers and other digital electronic devices.

The holder may be a complementary shape to receive the transparent tubeof the gas detector tube. The holder may also have a locating system foraccurately placing the gas detector tube in the electronic reader. Thelocating system has components that work in conjunction with componentsof the gas detector tube to allow for repeatably and accurately placingthe gas detector tube in the holder of the gas detector tube reader andmay be any components that are capable of aligning the gas detector tubein the reader as previously described.

Further embodiments of the optic-electronic gas detector tube reader arecapable of compensating for any effects on reading as a result ofrelative humidity, temperature and barometric pressure. Such embodimentsof the gas detector tube reader may comprise at least one environmentalsensor selected from a temperature sensor, a pressure sensor, or arelative humidity sensor; wherein each sensor is in communication withthe central processing unit. A central processing unit of the gasdetector tube reader is capable of estimating a concentration of targetgases in a sample from the length of stain and correcting the gasconcentration using compensation factors specific to the gas detectortube and the output of the environmental sensors.

Determination of a more accurate estimation of an actual concentrationusing gas detector tube should incorporate compensation forenvironmental factors. An embodiment of the optic-electronic gasdetector tube reader can read the calibration and compensation data fromeach gas detector tube. The calibration and compensation data, measuredconcentration and compensated concentration may be depicted on a displayon the optic-electronic gas detector tube reader and/or communicated toanother processing unit for display and recordation. The displayed orcommunicated data may include, but is not limited to, the type of tubein the reader, the target gases, measurable concentration range of thetube, tube accepted/rejected upon introduction of an internal standardand/or expiration date, concentration measured, ambient environmentalconditions including, but not limited to, relative humidity,temperature, barometric pressure, total % of compensation applied to themeasured gas concentration to determine a estimated concentration, aswell as other desired information. In an embodiment of the gas detectortube reader, the optically or electronically coded information read fromthe gas detector may be displayed prior to sampling to verify thecorrect tube is being used, followed by the measured data for theambient environmental conditions and tube acceptance.

Embodiment of the gas detector tube reader may comprise a sampling pumpor may be a separate unit independent of the sampling pump. Embodimentsof the gas detector tube reader comprise a holder for the gas detectortube having at least one illuminating source capable of providingillumination of the optically readable information and the reagent.Preferably, the illuminating source provides each of red, green, andblue colors with separately or in combination to produce white light.The gas detector tube reader will also comprise light sensors capable ofread individual colors separately or mixed as white light. In certainembodiments, the gas detector tube reader may comprises means forinputting the altitude above sea level of the sampling location such asa keypad or dial adjustable by hand to different altitudes withincrement 250 or 500 meters above sea level, for example, wherein eachincrement step corresponding to roughly 250 meters ˜3% or to 500 meters˜6% of the scale of read concentration values.

In a specific embodiment, the gas detector tube reader comprises atleast two light sensors and one illuminating light source on each sideof a reading head. The reading head comprises two halves (shells) thatare hinged together to from the holder to receive the gas detector tube.The shells comprising a locating system to accurately place the gasdetector tube adjacent to the light sensors and light source. In certainembodiments, a first light sensor is situated very close to the inletportion of the chemical reagent. This sensor may be used to read thecolor of the chemical reagent prior to sampling in an area close to theinlet plug. Before the sampling period the signal of this sensor iscompared to the expected level of this signal as determined from theelectronically or optically coded information on the gas detector tube.If the color of the reagent close to the inlet is outside an acceptablerange, the gas detector tube reader will indicate that the tube shouldnot be used. This ensures that the tube will still be able to accuratelymeasure target gas concentrations. If a gas detector tube is improperlystored its shelf life may be reduced.

A second light sensor may be situated along the length of the colorchange reagent. The information signal from the second sensor issummarized with the signal of the first sensor and thus suppliesinformation for the color intensity along the reagent layer. Practicallythe first sensor is very small lengthwise portion of the main sensorwhich is separated electronically and is able to read separately fromthe second main sensor or its signal could be added to the signal of thesecond sensor.

The colorimetric tubes can have linear dependence from theconcentration—linear-colorimetric tube (length-of-stain) or the entirevolume can change gradually to certain color more at the beginning andless at the end of the scale of the tube. In a regular case when thecolor after prescribed volumes falls within the readable scale, thereading system integrates the signal from first and second sensors andall lengthwise color change or all color change (color result as colorintensity or density whichever is more dependent from the exposure) andcompares these changes to a calibration curve data provided by theoptical code.

The lines of the light sources and the sensors may be situated atapproximately 45 degree angle from one another. For example, one line ofsensors and two lines of light sources (each one capable to generateseparate RGB color light) in each of the jaws. In bottom jaw 23, thereis a movable pin-lock which clicks into a special opening or notch inscales wing 14 a. As the opening 31 is placed on one only scale wing 14a there is no way for the tube to be put wrongly or misarranged.

Once the pump is activated and the air start flowing trough the tube thereagent layer 15 will start changing with the first portions of thesubstance of interest. Immediately after air with targeted substancestart flowing in that reagent layer the sensors 56 and 57 will startintegration of the signal and comparison to data already introduced byoptical code calibration. In a typical sampling operation, only onestroke of the piston pump will be required to read the target gasconcentration for the expected range of gas concentrations. Duringsampling, the output from the first sensor and the second sensor areintegrated. The integrated signal from sensors 56 and 57 and signal fromadjustable dial 51 (introducing correction for altitude) are transferredto Central Processing Unit (CPU) and processed to compensate opticallyread signal from the colorimetric tube and read such signal according togenuine calibration curve.

As the calibration of the tube is originally perform after production incontrolled and steady ambient conditions, the gas concentration readfrom the tube should be corrected for differences in the temperature andrelative humidity at the time of sampling. The environmental sensors forambient temperature, relative humidity, and barometric pressurecommunicate with the central processing unit to be process the outputaccording to calibration and validation data read from the gas detectortube reader.

The measured gas concentration may then be corrected based upon thebarometric pressure or altitude, ambient air temperature and relativehumidity. The corrected gas concentration of the target gases may beshown on Liquid Crystal Display (LCD) 80 as concentration units ppm ormg/m³.

In situations when the concentration of the sample gas is low and nosignificant color change is measured or observed on the reagent afterpassing a typical volume of sample through the gas detector tube (onestroke of a piston type sampling pump, for example), the gas detectortube reader may detect an insignificant or no color change and indicatefurther greater sampling volume is required to properly read the targetgas concentration. As the gas detector tube reader observes asignificant and readable color change, the sampling may be stopped andthe total sampling volume is integrated. In this way, a gas detectortube may be used for measuring low concentrations of the target gases.However, some types of gas detector tubes may not be used to measureconcentrations below their prescribed ranges.

The gas detector tube may also determine the concentration of gasesabove the concentration rage of the gas detector tube. If theconcentration rage is above the range of the gas detector tube for thetype and quantity of the reagent, the reagent may all be involved in thecolorimetric reaction prior to the end of the sampled volume. In such acase, the signal of the light sensors over time may be analyzed toestimate the gas concentration of the target gases. The integratedsignal for 100% color change is processed along with the time when 100%color change is achieved. This data is compared to a calibration curveand following the curve of vacuum/time performance of the sampling pumpto determine the sampled volume at the time of complete reaction, thecentral processing unit may calculate the uncompensated gasconcentration. In such case, the total quantity of target gases is known(the capacity of the reagent) and the sample volume is estimated. Oncethe volume is estimated, the concentration may easily be determined. Inother embodiments, the gas detector tube reader comprises a flow meterfor direct determination of the sampled volume.

As such, the gas detector tube reader may expand the applicable range ofmany types of gas detector tubes by allowing reading of target gasconcentrations outside of the range of the concentration span printed onthe scales for visual reading.

Further embodiments of the gas detector tube reader may comprise apumping pressure sensor between the sampling pump and the gas detectortube. The output of the pumping pressure sensor is in communication withthe central processing unit and may be used to estimate the flow ratethrough the gas detector tube. The pumping pressure sensor may indicatea low or no sampling flow situation if after a time period, 10-30seconds, for example, the pumping pressure sensor does not indicate asubsequent rise in pressure. A low or no flow situation may occur if thetips of the gas detector tube were not removed or the gas detector tubewas improperly installed, for example. The pumping pressure sensor mayalso indicate the end of the sampling cycle when the pressure returns tothe starting pressure prior to sampling and be used for leak checking intesting mode prior to sampling. The pumping pressure sensor may befluidly connected between pump intake and the tube reading outlet of thereader. In such embodiments, the gas tube reader may comprise a sealingmechanism for the outlet of the gas detector tube. The sealing mechanismmay be an o-ring, rubber socket or other attachment ensuring a tightseal and is forming cavity with very small dead volume connected fluidlyto the pumping pressure sensor.

The gas detector tube reader holder is capable of securing tubes withinthe reader holder. The holder may further comprise an adjustmentmechanism to allow tube adjustment and zeroing of the gas detector tubesagainst tube reading sensors and optical code reading device.

Embodiments of a method of determining a concentration of target gases,comprise placing a tube in an optic-electronic gas detector tube reader,electronically reading information from the gas detector tube. Themethod may further comprise performing a presampling test of the gasdetector tube and reporting an acceptance or rejection of the tube.Additionally, the method may comprise drawing a known volume of gassample through the gas detector tube and optically reading the length ofstain. After sampling, if applicable, the readout of theoptic-electronic gas detector tube reader may display informationincluding, but not limited to, a measured gas concentration, thecompensation factors to be applied to the measured gas concentration,each compensation factor determined from a measurement of the ambientconditions sensors including, but not limited to, temperature, relativehumidity and barometric pressure or altitude, for example.

Example Gas Detector Tubes and Gas Detector Tube Reader

Embodiments of the gas detector tubes 10 are shown on FIGS. 1A-E andFIG. 2. The gas detector tubes 10 comprise a sealed transparent tube 11,a chemical reagent 15 capable of a colorimetric reaction with a gaseouschemical compound within the sealed transparent tube 11, at least oneelongated extension 14 extending from the tube 11, and at least onelength of stain measurement scale on the extension 14.

The embodiments of FIGS. 1A to 1E depict various cross-sectional areasof the transparent tube 11 including circular in FIGS. 1-B and 1-C, andpolygon in FIG. 1-D and FIG. 1-F. The surface of the tube 11 is cleanand clear of markings in the area of the reagent 15 for visual orelectronic reading of the length of stain. The gas detector tube 10comprises a transparent tube 11 comprising at least one inert materialsuch as glass, acrylic, polycarbonates, copolymers of polyethylene andpolypropylene, polyesters, etc. The extensions 14 comprising scalesresemble wings (“scale wings”) 14 and 14 a are situated longitudinallyparallel to the main axis of the tube 11. The tube 11 may be readvisually and electronically. Visual reading is possible by using one ofthe four possible scales with divisions printed on scale wings 14 and 14a. Scales can be printed on both (top and bottom) sides of each scalewing 14 and 14 a. The divisions of the scales can be related todifferent units of measure and/or different sampling modes such as thenumber of sampling strokes of a sampling piston pump. On FIG. 1-A, twounits of measure are shown printed on scale 14 in ppm and scale 14 a inmg/m3 for one sampling stroke. On the back side of scale 14 and 14 asame units may be used for 2, 3, 5, or 10 sampling strokes, for example.There are no lines on the surface of the tube 11 in the area of thereagent. The gas detector tubes may further comprise a transparentcovering 16. Conventional gas detector tubes comprise a scale with linesdirectly on the tube over the reagent. Such conventional scales mayinterfere or can mislead visual reading or may impair the lightillumination and reflected light for optic-electronic reading.

Embodiments of the gas detector tubes 10 may comprise an adhesive 18 tostabilize the gas detector tube 10 in storage and transport. One ofscale wings 14 or 14 a, for example, may be attached by adhesive 18 to asurface of tube holder 19. Another version of preferred embodiment ofcolorimetric tube 11 shown as cross-section 1-C on FIG. 1 has onewing-scale only.

Another embodiment of the gas detector tube is shown in FIG s depictingmore details of the information printed on the wing-scales includingnumber of strokes 17 d, units of measure the concentration 17 e,expiration date, and part identification number (PIN). Further,optically readable information 17 containing data for electronic readingand for electronic compensation of readings is printed on the scalewings 14 and 14 a. The first divisions of scales 14 and 14 a begin at apredetermined by calibration distance from the back end of pluggingmaterial 12. On wing-scale 14 there is a side notch, recess or smallaperture 31 with round or oval shape (to match with a wire locking knot30 or similar means when tube is inserted into reading head 20 of thegas detector tube, shown further on FIGS. 4 and 5). The recess, apertureor notch 31 allows precise positioning of the tube 11 in the jaws orshells of the holder of the gas detector tube reader. The light andoptical sensors of the reading head shown further in perspective view onFIG. 3.

FIG. 3 depicts an embodiment of the reading head of the optic-electronicreader of the present invention. The reading head 20 comprises two mainparts—upper jaw 22 and bottom jaw 23 which when closed are forming acylindrical cavity or holder having a secure fit with gas detector tube11, shown on the cross-section 3-B. On the bottom jaw, a locating systemcomprising an opening 32 in which a pin-lock 30 is capable of beingmoved up and down to thereby to click in the aperture 31 on the scalewing 14 a when the tube is introduced into the cavity between top 22 andbottom 23 shells. The tube thus precisely placed for furtherillumination and reading.

In each jaw, two long illuminating sources 58 are positioned forilluminating the colorimetric gas detector tube inside of cylindricalcavity of the holder. As shown in FIG. 3-B, the cross-section of thereading head shows the position of the tube in the cavity. Both upperand bottom illuminating lines have axis angled approximately at 90degree and approximately 45 degree to the main axis of the line of lightsensors 56 and 57. Thus the light emitted from sources 58 illuminatesthe surface of the reagent layer 15 and penetrates deeper. The amount ofreflected back light depends on the absorption and the dispersion of thelight in the layer. Both of absorption and dispersion depend at least inpart upon the color change of the reagent resulted from particular colorreaction. The nature of color reading with linear light source andlinear sensors suggest type of reading different from length-of-stainvisual or electronic reading. As far as the linear sensor observes thecolor change over predetermined length as % of the total reflectedlight, for electronic calibration purposes a sharp front or leading edgeof discoloration is not required. The reflected signal from the opticalsensor will integrate color changes over the illuminated lengthregardless of whether color changes have sharp front or changesgradually in the total volume. At predetermined sampling volume thesignal for reflected color-change and/or change of density isproportional to the sampled concentration. This is the base of maincalibration mode—predetermined sampling volume. Embodiments of the gasdetector tube reader are capable of determining the concentration oftarget gases based both on the length of stain and the color or colorintensity of the reagent after exposure to target gases.

The signal generated by the sensors 56 and 57 may be proportional to theconcentration of reflected light form the reagent. On the basis of thissignal, the CPU would generate value of concentration comparinggenerated signal to the values from calibration curve. Those values aresupplied to CPU by optical coded information 17 superimposed on one wing14 and read by optical reading means 70 on FIG. 3. The optical codereading process my take place at the moment of inserting the tubethrough front slot of the reader head into cylindrical cavity formedbetween upper 22 and bottom 23 jaws. The view of the tube beforeinsertion into the reading head is shown on FIG. 4. After insertion thetube is shown on FIG. 5. The inserted tube is secured by locking knot 30and positioned into reading head. At the same time other compensatorysignals are generated and transferred to CPU 50 to signal for altitudecorrection from dial 51, signals from temperature sensor 28 and fromhumidity sensor 24 shown on FIGS. 4, 5, 6. The sensors for temperature28 and relative humidity 24 are placed in close proximity to the frontpart of the reading head and have access to ambient air. In thisembodiment, the altitude above sea level for the sampling operation isinput by the personnel performing the sampling process, therefore signalfor altitude could be and is generated by hand driven potentiometer/dial51. Small deviations of the local pressure due to weather factors areusually much smaller than 1% of the local barometric pressure and may beneglected.

A sensor for pumping pressure 25 and pressure drop (from theenvironmental pressure sensor) on FIG. 5-A is fluidly connected to thespace between a front rubber socket or other seal 27 of the pump andfront of the pump piston 43 The pumping pressure sensor is electricallyconnected to CPU 50. The pumping pressure sensor 25 generates signal forvacuum and has two functions: to signal for predetermined pressure dropwhen piston is locked back for pump test and to determine whether socket27 is filled by a tube 11 without broken tips, for example. In apressure test if pressure signal doesn't change for a predeterminedtime, the CPU may indicate a good seal on the LCD-display 80 and send asound signal that the pump and the system are considered reliable andsampling can be performed. The CPU can also send signal for malfunctionif the pressure signal does not change during a sampling operation.

Another function of pumping pressure sensor 25 is to indicate the end ofthe sampling stroke and send signal for that to CPU. Sensor 25 may haveadditional function to send signal for sudden pressure drop (malfunctiondue to rupture or other causes) during the sampling period and thepumping pressure sensor may count the number of strokes of the pump andcalculate a sample volume, for example.

Besides the described main sampling mode where tube is used within itsnormal concentrations span two other modes are possible:

If the concentration is significantly higher than the exposureconcentration span calibrated for 1 stroke, the CPU will stopintegrating the reflected signal at the point when this signal shows100% color saturation. As the time of one (or more) stroke cycle isintroduced by optical code, CPU estimates concentration on the base ofsampled volume necessary for 100% color saturation (determined bycalibration). LCD display will show concentration value along with asymbol (star) marking that the value is approximated.

If the concentration is very low and no signal for color change isgenerated during regular stroke cycle the CPU can urge for more strokes(2 to 10 if certain tube allows approximation of this type). The finalconcentration will be calculated by CPU on the base of larger sampledvolume for achieving predetermined color results. The value of theconcentration will be displayed with symbol showing that the value isapproximated.

Signals from different sensors may be used for compensating for ambientconditions known to have influence on the value of the determinedconcentration. The factors obtained during the calibration andvalidation process of the tube and respective correction data along withdata for hermeticity of the system are transferred to CPU for processingwith the signals for other observable parameters such as theconcentration and correction factors. By pressing communication buttons82, 83 and 84 seen on FIG. 4 and FIG. 6 the values of measuredtemperature, relative humidity and calculated for certain temperatureabsolute moisture content can be obtained on display 80 as well as thevalue of entered by altitude compensation dial 51.

The aforementioned embodiment is connected and designed to be used withpiston type hand pump shown as assembly on FIG. 4 and as side viewcross-section on FIG. 5. The reading head 20 is enclosed intocylindrical enclosure 21 designed as extension of hand pump 41 andconnected to it by socket 42. The wings 14 shown in front are separatingtop and bottom jaws (not seen in this position). The tube 11 with brokenends is positioned into rubber inlet 27 which is fluidly connected tothe vacuumed space in pump 41 and with pressure drop sensor 25.

On the side view cross-section FIG. 5-B the tube 11 is shown preciselypositioned into the cavity by locking pin 30. The optical code 17 isread by the optical code reading means 70. Also, shown is an energysupply 60, CPU 50 and at the front of the reader are sensors 24 and 28.By pushing down pin head 29, the locking pin 30 is going down andinserting the tube 11 is possible. At the beginning of this insertionoptical reading means 70 are reading the optical code 17. Top and bottomjaws on both sides of scale wings are not shown here for simplicity.

The process of reading and data integration of the reader assembled withpiston type pump 41 and the main interconnections are shown aselectronic schematic diagram on FIG. 6.

The process of pump-vacuum cycle(s), moment of reading and integrationare shown on FIG. 7-A to C. When the sampling process is according toexpected concentrations span the color change is read after the END ofone or more predetermined count of strokes. The printed on the tubevisual information as well as optical coded one will urge to appropriatestroke numbers (one stroke is considered most common case). The curvesrepresenting vacuum as a function of time laps FIG. 7-A for two basicstyles of hand pumps (bellows and piston pumps) are different. Thisdifference is a result of type of vacuum characterizing both pumpstyles. As seen on FIG. 7-A piston pump develops high vacuum at the verybeginning and it gradually drops to atmospheric pressure for full timestroke. The bellows pump style develops lower and moderate vacuumlasting till the end of stroke. As the fluid velocity governed by thelevel of vacuum is different during the stroke, the calibration curvesfor both pump styles have some differences. The integrated area underthe vacuum curves for both pumps represents the sampled volume and isusually the same—100 ml. per stroke. On this FIG. 7-A is depicted theprocess of reading very high concentrations exceeding tube calibrationspan for visual reading. There are shown two points—B/B1 representingrespectively the positions when the color change rises to 100% and theprocess of integration of color change stops. The sampled volume couldbe different even with same type of tubes. This fact explains why atvery high concentration the point B—unbroken line (for piston pump) hasdifferent time lap from point B1—dashed line (for bellows pump).

The CPU uses the time laps corresponding to points B/B1 to generateestimated concentration data, based on preliminary exposure datatransferred by optical code 17.

At very low concentrations on FIG. 7-B the sampling volume ofrecommended one (or more strokes) may be not enough to generate colordetectable from the first sensor 56 (FIG. 3). The sampling may bestopped or the reader can urge on the LCD-display for more strokes ifthis low concentration can be measured by??? certain type of tube byincreasing the sampled volume (more sampling strokes). The process maytake several strokes until first readable signal from sensor 56 issufficient. The sampling stops at points C/C1 on FIG. 7-B. If a propercalibration is done the reading may be successful. Not all types oftubes allow such calibration and approximation.

FIG. 7-C describes the process of vacuum check for piston pump. Vacuumis checked by sensor 25 (FIGS. 5 and 6). The vacuum should be stable forcertain period of time illustrated by curve between points D and E. Ifthe vacuum drops to any point below E such as point F the seal is notvacuum tight and sampling may not be accurate. The reader will givecorresponding sound and light signal. If the vacuum detected by sensor25 suddenly drops to zero during the sampling cycle the reader shouldabort sampling process and give audible and/or visual signal.

The calibration can be very successful at all type conditions. One andsame type of tube can be used and read with different types pumps if thecalibration conditions are introduced by optical code 17 for the usedtype of pump.

It is in the spirit of the present invention to use the same type ofreading approach with any type of sampling pump used with colorimetrictubes such as bellows pump or piston pump. None of the main features orschematic diagrams needs to be changed except the way of connecting thepump to reader and way of calibration. As far as the bellows pumpdelivers much lower but more permanent vacuum which is the driving forcein the sampling process—only calibration curve of the tube need to bechanged.

The present invention suggests a system of two parts—tube and tubereader, each one having unique features and unique advantages. Thedesign of the colorimetric tube allows the tube to be sampled and readvisually or by suggested electronic reader which is impossible with allmarket available tubes. The design with wing-scales is advantageouspermitting up to four scales for different sampling conditions anddifferent units of measure. The design allows tubes to be much moresafety in use and easy to transport and package. The design suggestsalso tubes with flat sides for easy reading avoiding reflection ofcylindrical surface. The design assumes use of transparent plasticswhich is a big safety and manufacturing feature decreasing alsomanufacturing costs.

The design of tube reader advantageously suggests besides reading thecolor corresponding to certain exposure doses self introduction of thecorrection factors for temperature, humidity and altitude which willmake final result much more reliable. The tube reader will allow readingof very low and very high concentrations beyond the calibration spanprinted on the scales.

The embodiments of the described gas detector tubes, gas detector tubereaders and methods are not limited to the particular embodiments,components, method steps, and materials disclosed herein as suchcomponents, process steps, and materials may vary. Moreover, theterminology employed herein is used for the purpose of describingexemplary embodiments only and the terminology is not intended to belimiting since the scope of the various embodiments of the presentinvention will be limited only by the appended claims and equivalentsthereof.

Therefore, while embodiments of the invention are described withreference to exemplary embodiments, those skilled in the art willunderstand that variations and modifications can be effected within thescope of the invention as defined in the appended claims. Accordingly,the scope of the various embodiments of the present invention should notbe limited to the above discussed embodiments, and should only bedefined by the following claims and all equivalents.

1. A gas detector tube reader, comprising: a holder for receiving a gasdetector tube; an information reader capable of reading electronic oroptically coded tube information on the gas detector tube; an opticalreader capable of determining the length of stain in the gas detectortube; and a central processing unit.
 2. The gas detector tube reader ofclaim 1, comprising: at least one environmental sensor selected from atemperature sensor, a pressure sensor, or a relative humidity sensor;wherein each sensor is in communication with the central processingunit.
 3. The gas detector tube reader of claim 2, wherein the centralprocessing unit is capable of estimating a concentration of target gasesin a sample from the optically determining at least one a length ofstain, color change, and optical density of the reflected light andcorrecting the concentration using compensation factors based upon theoutput of the environmental sensors to determine an correctedconcentration.
 4. The gas detector tube reader of claim 1, wherein theholder and gas detector tube comprise a locating system for accuratelyplacing the gas detector tube in the gas detector tube reader.
 5. Thegas detector tube reader of claim 4, wherein the locating systemcomprises a pin and a recess.
 6. The gas detector tube reader of claim1, wherein the information reader is one of an optical reader or a radiofrequency identification reader.
 7. The gas detector tube reader ofclaim 6, wherein the tube information comprises at least one of a typeof tube, target gases reactive with the reagent, limits of the gasconcentration range, a calibration curve, an expiration date, anunreacted or pristine color of the reagent, and an allowable colorchange range for the reacted reagent, environmental correction factorsof curves for the reagent, an expected color change and colordensity/saturation of the reacted reagent.
 8. The gas detector tubereader of claim 1, comprising: a temperature sensor in communicationwith the central processing unit; and a relative humidity sensorcommunication with the central processing unit; wherein the electronicor optically coded tube information includes a correction factor orcurve for both temperature and relative humidity.
 9. The gas detectortube reader of claim 8, comprising: a barometric pressure sensor inelectrical communication with the central processing unit; wherein theelectronic or optically coded tube information includes a correctionfactor or curve for both temperature and relative humidity.
 10. The gasdetector tube reader of claim 1, comprising: a pump connector forattaching a detector tube sampling pump to the gas detector tube reader.11. The gas detector tube reader of claim 10, comprising a seal forcreating a sealed connection between the gas detector tube and the gasdetector tube reader.
 12. The gas detector tube reader of claim 11,comprising a pumping pressure sensor in fluid communication with aconduit between the pump connector and the seal, wherein the pumpingpressure sensor is in communication with the central processing unit.13. The gas detector tube reader of claim 1, wherein the optical readercomprises at least one illuminating light and at least one opticalsensor capable of distinguishing between colors.
 14. The gas detectortube reader of claim 13, wherein the holder comprises two jaws forsecuring the gas detector tube between the jaws.
 15. The gas detectortube reader of claim 14, wherein the optical reader comprises at leastone illuminating light and at least one optical sensor capable ofdistinguishing between colors on each of the jaws.
 16. A gas detectortube, comprising: a sealed transparent tube; a chemical reagent capableof a colorimetric reaction with a gaseous chemical compound within thesealed transparent tube; at least one elongated extension extending fromthe tube; and at least one length of stain measurement scale on theextension.
 17. The gas detector tube of claim 16, comprising atransparent plastic adhered to a surface of the transparent tube and asurface of the elongated extension.
 18. The gas detector tube of claim16, wherein the transparent tube does not comprise a length of stainmeasurement scale.
 19. The gas detector tube of claim 18, wherein thereis no indicia printed or etched on surface of the transparent tube. 20.The gas detector tube of claim 16, wherein the chemical reagentcomprises a porous solid with pathways that allow gas to flow throughthe porous solid.
 21. The gas detector tube of claim 16, wherein thereagent is retained within the tube between two porous plugs.
 22. Thegas detector tube of claim 17, wherein the transparent plastic isadhered to the tube by at least one of physical means, shrink wrapping,or adhesive.
 23. The gas detector tube of claim 22, wherein the adhesiveis a permanent neutral transparent adhesive layer.
 24. The gas detectortube of claim 17, wherein the transparent plastic is conformable to atleast a portion of an exterior of the tube.
 25. The gas detector tube ofclaim 16, wherein the extension is an elongated rectangular shape 26.The gas detector tube of claim 16, wherein the extension comprises apocket capable of receiving a member comprising at least one length ofstain scale.
 27. The gas detector tube of claim 16, wherein theextension extends along a length of the tube at least as long as adistance between the two porous plugs.
 28. The gas detector tube ofclaim 16, wherein the extension comprises indicia comprising bothvisually readable length of stain scale and an electronically readableinformation.
 29. The gas detector tube of claim 38, wherein theelectronically readable information comprises at least one of a type oftube, target gases, limits of the gas concentration range of thereagent, a calibration curve, expiration date, initial color of thereagent, allowable color change after certain edging, reagent colorafter contact with colorimetric reaction, color density/saturation ofthe reacted reagent, or expected color change and colordensity/saturation of the unchanged reagent material.
 30. The gasdetector tube of claim 16, wherein the visually readable informationincludes at least one of type of tube, range of exposure, recommendedvolume of sampled gas, expiration date, part and lot numbers, or anindication of the direction of flow during sampling.
 31. The gasdetector tube of claim 16, wherein the extension comprises a pocket, alength of stain scale is within the pocket and the length of stain scalecomprise both visually readable scale and an electronically readableinformation is printed on the scale.
 32. The gas detector tube of claim16, wherein the gas detector tube comprises a second extension attachedon an opposite side of the transparent tube as the extension.
 33. Thegas detector tube of claim 32, wherein the two extensions aresubstantially in the same plane.
 34. The gas detector tube of claim 32,wherein the two extensions are in different but substantially parallelplanes.